Picking the right backpack

Water resistance. I thought that one of the worst things that could happen is for all my belongings to get soaking wet if the weather decided to act all English. I had read on a number of sites that the backpack does not need to be 100% waterproof but making sure it has some resistance is a good idea.

Compartments. I wanted my bag to have a number of compartments so that I could separate some of my things to make sure they were easy to find.

Internal Frames. My friend traveled with a very old fashioned backpack that had poles on the outside. She said it was very uncomfortable and advised me against purchasing one like this even if it was cheaper.

Wheels. Although this is not a typical feature to many travellers backpacks, I decided to opt for this because I know I suffer with neck and back pain when carrying heavy bags which leads to migraines. My boyfriend also happened to travel Asia with a bag on wheels and was envied by many.

Padding. I made sure that the straps were padded so that if I needed to put it on my bag I wouldn’t be in so much pain.

Size. I considered what size to take very carefully because I did not want to not be able to fit the essentials in but also did not want to be able to take too much. I knew that if there was spare space I would have tried to fill it with things I did not need. I also had to consider the weight restrictions on my flight. 20kg is not a lot! I therefore decided to go for a 65 litre bag.

I am still not sure what size to take. I only have 20kg weight allowance on my flight but as I am traveling for quite a while I am sure I will acumilate more things. I am therefore not sure whether to opt for a smaller option for ease of transporting from place to place or opt for the bigger one so that I have the option to buy things and comfortably be able to fit everything in one bag. Any suggestions?